PROJECT SUMMARY Drug-induced cardiac toxicity and adverse events remain a major challenge for both industry as well as regulators. The current strategies for early identification of these potential liabilities in the drug discovery and development process involves a combination of in vitro assays, animal models and an extensive ECG-based cardiac repolarization study which is conducted on human subjects during Phase 2 clinical trial. These latter studies are known as ?Thorough QT? studies (TQT) since they have specifically focused on drug-related changes in the QT interval, a biomarker for cardiac repolarization and the induction of pro-arrhythmic cardiac activity. While these strategies have contributed in the identification of potentially dangerous pro-arrhythmic molecules, it is also becoming apparent that this approach is amenable to significant improvements. Recently, the leadership at the Division of Cardiovascular and Renal Products of the FDA Center for Drug Evaluation and Research has facilitated a number of initiatives aimed at soliciting the development and validation of novel experimental models for assessing cardiac safety of new drugs. As explicitly stated by the regulators, the goal is ?to replace the TQT clinical studies with one or more pre-clinical assays, by July 2015? (Dr. Norman Stockbridge, CSRC-HESI-FDA Meeting, July 24, 2013, Silver Spring, MD). Species differences create insurmountable limitations for all approached based on animal models. In addition, newer strategies relying on cardiomyocytes artificially derived from stem cells or iPS cells do not faithfully replicate all the physiological features of native adult human cardiomyocytes and do not model the effects of aging and comorbidities. AnaBios has recently developed a novel ex-vivo human heart-based drug safety evaluation platform, which is currently undergoing formal Biomarker Qualification at the FDA. The technology relies upon the utilization of viable human donor hearts in the laboratory for conducting ex-vivo measurements of cardiac action potentials to determine the arrhythmogenicity of new drugs. This approach was initially validated in Phase I using a set of 5 reference compounds tested in blinded fashion. We demonstrated the ability of this human ex- vivo assay to correctly discriminate pro-arrhythmic from non-pro-arrhythmic drugs. This new approach provides the next of kin to a human clinical cardiac study, but avoids the risks related to drug exposure in humans in the clinic, as well as the high costs and extended timelines which come with the clinical studies. The present Phase II proposal will fully leverage our ex-vivo human heart methods by further validating and refining the arrhythmogenicity model and by advancing the platform to a commercialization-ready stage that will permit service of a large number of drug safety evaluations. By providing researchers with the relevant human based safety data, we anticipate the services resulting from this Phase II project will transform cardiac drug safety assessment.